The most obvious evidence of that bravery is the nudity required by Shaffer's 1973 drama, a formalist, ritualistic play that traces a child psychologist's breakthrough with a violent young patient who was remanded by the English court after blinding several horses.

Since an ill-fated sexual encounter with a girl named Jill (the chirpy Anna Camp) is at the heart of young Alan Strang's problems, the nakedness required from Radcliffe is prolonged. And in an age when almost every item in an audience's pocket can take a picture, it surely required an admirable comfort level with both brand subversion and personal revelation.

But then, personal revelation is what "Equus" is all about.

Its central conceit is that Dysart, the psychologist who treats Strang, comes to envy the intensity of the young man's passions and to contrast them with the quotidian agonies of a prosaic, middle-age existence. The device of the shrink being in bigger trouble than the patient seems familiar, even hackneyed today, but Shaffer's much-copied drama was revelatory in its day. Here was a play that popularized some of the ideas that came out of those 1960s fringe-theater writhings in London and New York and added a literary bent to boot.

Thea Sharrock's production from London is a simple but nonetheless distinctive staging. It moves rapidly, balancing the sometimes-indulgent verbosity of the script. It is shrewdly lit by David Hersey—at one point, Alan's cold father ( T. Ryder Smith) looks like a hollow-eyed corpse. But only for an instant. The show is faithful to Shaffer's dramaturgical schemata—handsome, masked men play the equine characters and John Napier's stage design recalls a classical arena. Or maybe an operating theater.

Some audience members watch the action from an on-stage balcony, as if Sharrock was playing with the celebrity of her star, who literally gets peered at from all sides.

This is not some dazzling reinvention of the play—and the climax of the show doesn't pack the oomph it might. But many nuggets lie under its surface.

Including the casting of Richard Griffiths. Thanks to the movie, most people associate Dysart with Richard Burton—a handsome man whose fall toward desperation felt like a celebrity going on a bender.

Griffiths is a movie star himself. But he's a very different physical type. He moves awkwardly—and he backs away from the script's opportunities for verbal flourish, leaning into his lines reluctantly. Some of them almost get lost in his cigarette smoke.

Perhaps Griffiths goes too far in that direction. But the effect of this very fine performer's work is to show us a Dysart with a great deal at stake. You believe he's on the edge. You believe the story of two naked teenagers would fill him with excitement and existential terror. And thus, as Shaffer surely intended, you start to realize you scratch only the surface of the limited passions of your own life.